Baca announced Tuesday he will step down at the end of the month. The move comes amid several scandals in the Sheriff's Department and an ongoing federal investigation into deputy abuse in the jails.

County Supervisor Gloria Molina, who had been Baca's most vocal critic on the board, said of the sheriff's resignation: "It was very shocking and very surprising. It certainly caught me off guard."

Molina said she thought Baca had "trusted people a little more than he should."

"I think there was a second tier of management that had tremendous problems," she said.

She also faulted the sheriff for not moving to crack down on problems in the department before they reached crisis level: "It doesn't have to fall apart before we fix it, and unfortunately things were falling apart for a number of years."

Los Angeles Police Chief Charlie Beck told reporters Tuesday the decision to retire was “very difficult” for Baca, whom he called a “friend and mentor.”

“People who are in aspects of leadership in law enforcement have to realize that sometimes you have to do things that are in the best interest of the organization above your own self-interest,” Beck said. “And I believe, based on what Lee has told me and what I know about him, that this is why he did this.”

“He believed that all the fury and fire surrounding him had caused his department to be impeded from doing its job. And that’s why he stepped aside,” Beck continued. “He’s a great man. He’ll be known as a great sheriff -- mark my words -- but that is an extremely difficult job.”

Los Angeles Mayor Eric Garcetti echoed those sentiments, calling Baca’s decision “the right move for himself and for his department.”

Beck and Garcetti said they hoped Baca’s successor would be a strong partner to the LAPD, someone who would work to reduce crime levels and focus on regional security.

They also emphasized the importance of a sheriff who values transparent policing. Garcetti said he would look for a “reformer that can make sure the Constitution is respected and individual rights are respected at every level of the criminal justice system.”

Beck agreed.

“I look for somebody that’s collaborative. I look for somebody that has a good sense of transparent, constitutional law enforcement and I look for somebody that will be my partner,” Beck said. “These are the two biggest law enforcement agencies west of the Mississippi, and we have to work together.”

Baca has been sheriff since 1998, and had forged deep ties with diverse communities, but he has faced a drumbeat of scandals recently.

His announcement came a month after federal prosecutors filed criminal charges against 18 current and former sheriff's deputies accused of beating jail inmates and visitors, trying to obstruct the FBI in an investigation of corruption inside the nation's largest jail system, and other crimes.

Baca was also coping with searing criticism of his leadership from a blue-ribbon commission appointed by the Board of Supervisors to examine allegations of jail abuse.

Last year, the U.S. Department of Justice accused sheriff's deputies of engaging in widespread unlawful searches of homes, improper detentions and unreasonable force as Antelope Valley authorities conducted a systematic effort to discriminate against African Americans who received low-income subsidized housing.

More recently, The Times also reported that the department had hired dozens of officers in 2010 despite background investigations that found they had committed significant misconduct.

At the news conference Tuesday, Baca — who spent 48 years with the department, including 15 as sheriff — was at times emotional as he explained his decision, which he said he made three days ago.

"I will go out on my terms," Baca, 71, said. "The reasons for doing so are so many, most personal and private."

Baca insisted his decision to step down was "based on the highest of concern for the future of the Sheriff's Department." He repeatedly cited the upcoming campaign, which he said had already brought a "negative perception" to the agency.

"I don't see myself as the future," he said. "I see myself as part of the past."

He said his greatest accomplishment would be reducing crime rates, and he commended his deputies for their work.

“They have conducted themselves with the utmost integrity and professionalism resulting in yet another year of historic crime reductions in nearly half a century,” he said. “In my opinion, your Sheriff’s Department is the greatest law enforcement agency in the world.”